Conventionally, cryogenic units for the separation of gases comprise at least one distillation column which is disposed within an insulating structure called a cold box. The cold box typically has a substantially parallelepipedal shape so as to provide a predetermined thickness of insulation around the column. It is typical for the cryogenic distillation columns and all of the associated equipment (heat exchangers, cryogenic pumps, cryogenic valves, connecting pipes, etc.) operating at low temperature to be arranged within the cold box and then for the cold box to be filled with an insulator in loose bulk form, such as expanded perlite or compacted mineral wool. This insulator thermally protects each component from the external temperature and from that of other components which may be at different temperatures and heat leak that affects plant performance. This type of material derives its insulating properties from both low thermal conductivity (<0.05 W/m° C.) and a high head loss which is favourable in terms of the convection phenomenon.
Typically, in an effort to limit construction costs, and to maximize quality, the column is preassembled with tubing elements to as great of an extent as possible in the controlled environment of the shop. This preassembly usually consists of a framework corresponding to that of the future cold box, and of a cross section integrating the future insulation thicknesses all about the column. This is often completed prior to transporting and installing the assembly at the worksite. This is typically referred to as a “cold box package”. Apart from their weight and their dimensions, sharply driving up the cost of transportation, such completely preassembled assemblies are confronted with serious transportation problems (e.g., difficulties clearing bridges, difficulties transporting the assemblies around corners . . . ) largely because of their great size. Also, equipment needed for lifting these packages is less available or extremely expensive. This is currently becoming a greater problem as the dimensions of the column are becoming greater, as dictated by the current need for massive production of gas.
An alternative would be to assemble and erect the column, cold box and the ancillary components entirely in the field. This will reduce the transportation issues, and possible reduce issues with misalignment and interconnection of fittings. However, utilizing this route allows the construction process to become vulnerable to variations in the weather, material delivery delays, issues involving labor shortages, and possible quality control problems.
Therefore, there exists a need in the industry for a solution that will allow the above problems to be circumvented.